bad first day

So I finally got my boat in the water. The thing fires right up. We cruise out to the middle of the lake, eat lunch, go to fire it up to get in a few sets. And it won't start. After frustration and inexperienced tinkering, it finally starts after about 25 minutes of trying to crank over. The baby on board is cranky by this time so we decide to take her and Mom in while the rest of us try to get a set in. Get to the dock, unload baby, engine dies and won't restart. Batteries are fine, they are cranking the engine fine. It just won't start. So we trailer it up and head home. Any symptoms sounding familiar, any solutions to offer?